A landslide has buried 18 children and one adult in a mountainous area of south-western China that was hit by earthquakes and flooding a month ago, state media have reported.

Chinese officials said the Youfang primary school collapsed when the landslide struck the village of Zhenhe in Yiliang county, Yunnan province, at around 8am on Thursday morning. Eighteen students are thought to have been inside.

Zhenhe village in Yunnan province, China

An adult was also trapped when two houses in the village were toppled, according to the statement published on the county website.

State news agency Xinhua said a family of three managed to escape. It added that other residents had been evacuated from the area. An official from the county told Associated Press on Thursday that rescuers had arrived at the village.

The students would not normally have been at school this week due to a national holiday. But Li Zhong, head of the county education bureau, told the China News Service they were making up for classes suspended after two earthquakes hit the area in early September.

That disaster, which saw shockwaves of 5.7 and 5.6 magnitude, claimed 81 lives and injured 800 people in Yiliang and neighbouring areas. It was followed by torrential rain that triggered floods and mud and rockslides through the area – damaging roads and relocation sites for emergency services.

The central government said at the time it had allocated 1bn yuan (£100m) for disaster relief in the county and premier Wen Jiabao visited to inspect rescue work.